Static Friction and angle of Repose

I did an experiment where I had to determine the static friction of a wooden block on a horizontal wooden plank.

I determined Mu s for that to be 0.246

I then used the same block and plank, but this time I tried to determine Mu s by increasing the angle between the plank and the horizontal. I basically raised one side of the plank until the block started sliding...and recorded that angle as the angle of repose. I got Mu s for this part of the experiment to be 0.306

now I had to calculate the percent difference: ((.246-.306)/average) * 100

and I got 21.69 %

Shouldn't the percent difference be as small as possible? I assumed that Mu s would theoretically be the same no matter what angle?

If you were maintaining constant speed you were measuring kinetic friction that is always less than static, the point at which it begins to slide.

Other sources of error are not pulling exactly horizontal for instance. Slightly up lightens the loading, down increases the loading. Or measuring the angle ± a degree or so, as you tilt it, etc. Or reading the scale as you are pulling. etc.

Although I'm doing some fast hand waving about repeatability and error, someone of your level, with what I expect to be your equipment, should probably only use one significant figure for wood on wood.